1. Field Of The Invention
The present invention relates to a body-weight adjusting device for use with a vehicle seat suspension.
2. Description Of The Prior Art
It is known to be desirable to provide a vehicle seat, especially for a driver, with a seat suspension capable of a height adjustment in accordance with the weight of the occupant.
Hitherto, it has been proposed to provide a device capable of such an adjustment, a typical one of which will be described with reference to FIG. 1 and 2 of the accompanying drawings. In FIG. 1, (1) and (2) refer to an upper frame and a lower frame, respectively, of a seat. Lower frame (2) is formed substantially in a rectangular shape and made of a metallic frame substantially -shaped in section with the opening defined in the thus -shaped frame being faced to each other inwardly of the frame. Upper frame (1) is basically formed in a flat, plate-like shape with both the laterial portions thereon, or the optionally required portions thereof, being bent downwards. The frame is made of a metallic material of a configuration substantially conforming to that of lower frame (2). To this upper frame (1), a cushion member is mounted, using what may be termed a "cushion pan" (now shown).
Between upper frame (1) and lower frame (2), there is interposed a pair of X-shaped links (3) which constitute a seat suspension. This seat suspension is of a well-known type and comprises two links (4) and (5) rotatably, pivotally supported at pivot means (6) substantially centrally of each link. Upper end portion (5a) of link (5) is rotatably fixed by pivot means (7) to upper frame (1) rearwardly of the links, whereas lower end portion (4b) is rotatably fixed by pivot means (8) to lower frame (2) with the other lower end portion (5b) being slidably secured to lower frame (2) by means of a roller (9), or the like, so as to be movable forwardly and rearwardly relative to lower frame (2). The forwardly-located upper end portions (4a) of X-shaped links (3) are coupled by means of a rod (10) extended therebetween, thereby supporting the forward portion of upper frame (1) in a direction from the bottom of the seat. The rearwardly-located upper end portions (51) are coupled by means of a frame member (11) to which a pair of tension springs (12) are secured one at each end thereof.
With reference to both FIGS. 1 and 2, a bell crank (14) is rotatably fixed by pivot means (13) to the inner surface of upper frame (1) in such an arrangement that one end portion thereof is engaged with a nut (21) of an adjusting spindle (15) while the other end portion thereof is rotatably connected to one end of a tension frame (16) by means of pivot means (17). Tension frame (16) is connected at the other end thereof to the center portion of an equalizer frame (18) by pivot means (19) so as to be rotatable about said pivot means. Equalizer frame (18) is secured at both ends thereof to the other ends of the foregoing pair of tension springs (12), respectively. Adjusting spindle (15) consists of a rotary shaft with a thread (20) partially formed thereon, nut (21) being engaged with said thread.
Substantially at the center of the thus-constructed seat, a shock absorber (22) is arranged such that the one end thereof is rotatably affixed to the rear frame section of lower frame (2) and the other end is rotatably fixed to rod (10).
Several drawbacks or disadvantages are associated with the above-described conventional device. Springs (12) cannot be spaced apart from each other to any large extent. Consequently the relatively closed spaced springs (12) do not provide a stable adjustment of a seat suspension when a heavy weight load is applied to the seat. In addition, for adjusment of the seat suspension to accommodate a heavy occupant, adjusting spindle (15) must be rotated manually quite a number of times. For example, when it is desired to adjust the seat suspension for a variation in an occupant's weight from 50 kg up to 100 kg, adjusting spindle (15) must be rotated approximately 16 times. Moreover, rotation of the spindle become more difficult as the required adjustment approaches 100 kg. Consequently, operation of the foregoing seat adjusting means is extremely poor. Furthermore, it is be noted that adjusting spindle (15) is inaccessible when the door of the vehicle is closed.